Upstairs' trading draws more big investors

Big players change tactics in a fragmented market

Some of the world's biggest investors are changing the way they trade in US markets in response to what they say are rising risks for institutions of their size.

The strategies include conducting more "upstairs trades," in which deals are executed among big institutions, bypassing the broader market, as well as other sophisticated order-routing techniques designed to avoid pitfalls that have become increasingly apparent to investment managers.